reproducible .pyc files (& python-for-android)

[Felix C. Stegerman]

* "Bernhard M. Wiedemann" <bernhardout at lsmod.de> [2021-01-04 12:48]:
> This is not a timestamp issue, though. If those are varying, they are in
> the header (first 12 bytes) of the .pyc.
> 
> 
> │  000000f0: 6d5a 0d62 6469 7374 5f77 696e 696e 7374  mZ.bdist_wininst
> │ -00000100: 5a05 6368 6563 6b5a 0675 706c 6f61 644e  Z.checkZ.uploadN
> │ +00000100: da05 6368 6563 6b5a 0675 706c 6f61 644e  ..checkZ.uploadN
> 
> 
> I have seen this before and remember something about python string
> reference counters being dumped into these pickle files and that varied
> from ordering, so that
> py_compile py1.py py2.py
> produced different results than
> py_compile py2.py py1.py
> 
> One way to get reproducible results is to delete and recreate all .pyc
> files with
> find -type f -a -name "*.py" -print0 |
>   sort -z |
>   xargs -0 $python_binary -m py_compile
> 
> 
> Maybe related: creating .pyc files on i586 and x86_64 (with identical
> toolchain) always produced different results for me.

I was finally able to reproduce this on another machine.  This
particular difference is caused by whether the system has liblzma-dev
installed or not (when Python is built).

- Felix